1. Field of the Invention
This invention relates generally to apparatus in which video signals recorded in successive parallel tracks extending obliquely on a magnetic tape are reproduced by means of at least one rotary magnetic head which scans the tracks in succession at a rate dependent on the speed at which the tape is moved longitudinally by a tape transport assembly, for example, as in a so-called VTR, and more particularly is directed to providing such apparatus with an improved track searching arrangement by which the tape can be accurately and rapidly positioned for scanning of a selected track by the rotary head or heads.
2. Description of the Prior Art
When an existing magnetic video tape recorder or VTR of the helical scan type is operated in its reproducing or playback mode with a time base corrector, the speed at which the tape is transported or moved longitudinally between the supply and take-up reels may be varied while the rotary magnetic heads are rotated at the frame frequency so as to provide, on a monitor, a still, slow-motion or fast-motion reproduced picture in dependence on the speed of movement of the tape. Existing VTRs have been provided with a so-called joy-stick control knob or lever in addition to the usual playback or reproduce push button. When the playback push button is depressed, the normal reproducing or playback mode is established during which the tape is transported in the forward direction at a normal or standard speed. When the track searching mode of the apparatus is selected, the speed and direction of movement of the tape are determined by the extent and direction, respectively, of angular displacement of the joy-stick control knob or lever from a neutral position corresponding to no movement of the tape. A VTR provided with the foregoing joy-stick control knob or lever may be used for arbitrarily selecting a particular track on the tape at which a recording or reproducing operation is to be commenced, as during editing of the tape. The high speed movement of the tape in one direction or the other can be effectively achieved by a corresponding large angular displacement of the control knob or lever from its neutral position so as to bring a roughly desired portion of the tape to the position for scanning of the tracks thereon by the rotary head or heads, whereupon, the angular displacement of the control knob from its neutral position is reduced for correspondingly slowing down the movement of the tape and observing the successive pictures displayed by the monitor until a particular or desired field or frame of the video signals is located, at which time the tape movement is halted by returning the joy-stick control knob to its neutral position.
However, in the above described existing apparatus, the joy-stick control knob is associated with a variable resistor or a multi-contact switch included in the circuit for controlling the direction and speed of movement of the tape, and it has been found that such variable resistor or multi-contact switch is a source of frequency difficulties or defects in operation due to insufficient electrical contact between its relatively movable parts so that the existing apparatus is burdened by relatively poor reliability and a short operating life.
Further, in the described existing apparatus, the speed and direction at which the tape is driven upon selection of the track searching mode is determined by the position of the joy-stick control knob or lever at the time such selection is made. Accordingly, if the apparatus is changed-over from its playback mode to its tape searching mode at a time when the joy-stick control knob is disposed at a position corresponding to a fast movement of the tape in the forward or reverse direction, the resulting fast movement of the tape at the commencement of the tape searching operation may result in the uncontrolled movement of the tape pass the point at which the tape movement is to be halted for editing or for still-motion reproduction. Accordingly, in the existing apparatus, it is necessary to preset the joy-stick control knob to its neutral position for halting the movement or transport of the tape, or to the position of the knob corresponding to transport of the tape in the forward direction at the normal or standard speed, prior to change-over of the apparatus from its playback or reproducing mode to its track searching mode. Thus, the existing apparatus can be troublesome and relatively complicated to operate.